1. Field
The exemplary embodiments generally relate to a method for controlling the load variations, in particular load reductions, in a gas turbine.
2. Brief Description of Related Developments
The use of gas turbines normally consisting of a multiphase compressor, in which air sucked from the outside is compressed, a combustor, in which the combustion takes place of gaseous fuel added to the compressed air, and a turbine or expander, in which the gases coming from the combustor are expanded, is known for the production of electric energy. The turbine is therefore capable of generating mechanical energy which can be exploited for driving operating machines or for charging electric generators, such as for example, one or more alternators.
A gas turbine destined for the production of electric energy must consequently be able to face sudden disconnections from the electric supply, which can be due, for example, to particular circumstances or inefficiency which can arise in the electric supply. In a situation of this kind, the turbine must be brought to an anomalous but stabile functioning condition, in which the nominal rotation regime is reached, but the alternator does not supply power (a functioning condition called “full speed no load”), until the voltage is re-established in the outside electric supply to restart the service, i.e. reconnection with the electric supply.
During this disconnection phase with the supply, a so-called “load rejection” procedure must be activated as soon as possible, to immediately reduce the power and rotation regime of the turbine to a sufficiently low value so that at least one alternator can self-charge the auxiliary services of the machine or plant to which it is connected. The load rejection procedure is particularly critical for a gas turbine of the double shaft type, as the mechanical inertia of the turbine itself is extremely low and the corrective actions for preventing reaching an excessive rotation regime must be rapid and effective.